Cost-Effective Industrial Energy Systems : Multiperiod Optimization of Operating Strategies and Structural Choices

Abstract: It is of great importance to encourage the development of cost-effective industrial energy systems as the potential for saving energy and capital in industrial applications often is substantial. The MIND method has been developed for multi-period cost optimization of industrial energy systems. The optimal operating strategy of the industrial utility and production systems in co-operation can be found. Existing equipment units can be represented as well as new equipment structures. The representation of process units is performed in a way that facilitates the analysis of processes from various industrial branches. The production processes can be represented at the desired level of accuracy, i.e. one modelling unit may represent an equipment or a whole process line, Parts of the process system may then be represented with a higher accuracy. Since both energy and material flows are included, the interaction between the utility system and the production system can be studied. Nonlinear relations, found in expressions of energy demand, energy conversion efficiency and investment cost, are linearized in mixedinteger linear programming. A flexible time scale facilitates the performance of long and short term analyses. The optional time scale allows variations in boundary and process conditions to be represented. The MIND method has been applied to several industrial energy systems. The optimal operating strategy of a pulp and paper mill and a refinery showed opportunities of considerable capital savings. In the case of the refinery, possibilities for energy recovery measures, calculated by Pinch Technology, were also included in the optimization. Calculations show that MIND can be combined with other analysis methods and that the combination yields new insights in the total energy system. In this thesis, the introduction and the literature survey of related work are followed by a description of the method and a chapter of comments to the enclosed papers. The following papers are included and will be referred to in the text (I - VI): (I) Nilsson, K. and Soderstrom, M. "Optimizing the operating strategy of a Pulp and Paper Mill using the MIND method", Energy- The International Journal, Vol. 17, No. 10, pp. 945 - 953, 1992. https://doi.org/10.1016/0360-5442(92)90043-Y (II) Nilsson, K., Soderstrom, M. and Karlsson, B.G. "MIND optimization reduces the system cost at a Refinery", Accepted for publication in Energy - The International Journal, 1993. (III) Nilsson, K. and Soderstrom, M. "Industrial applications of production planning with optimal electricity demand", Applied Energy, Vol. 46, No. 2, pp. 181-192, 1993. https://doi.org/10.1016/0306-2619(93)90067-Y(IV) Nilsson, K. "Industrial production planning with optimal electricity cost", Energy Convers. Mgmt., Vol. 34, No. 3, pp. 153 - 158, 1993. https://doi.org/10.1016/0196-8904(93)90131-S(V) Nilsson, K. and Sunden, B. "A combined method for the thermal and structural design of industrial energy systems", Recent Advances in Heat Transfer (Eds. B. Sunden and A. Zukauskas), 1017-1024, Elsevier Science Publisher, Amsterdam, 1992. https://libris.kb.se/bib/4952922(VI) Nilsson, K. and Sunden, B. "Optimizing a Refinery using the Pinch Technology and the MIND method", Accepted for publication in Heat Recovery Systems & CHP, 1993. https://doi.org/10.1016/0890-4332(94)90011-6